calculate a message digest (checksum)
for a file
These utilities take as input a message of arbitrary length and produce as output a message digest (checksum) of the input.
Two messages having the same message digest (a collision) have been produced for MD5 and for SHA-1, so their use is deprecated.
The options for use with each command are as follows:
- Output checksums in base64 notation, not hexadecimal.
- Compare the checksum of each file against the checksums in the checklist. Any specified file that is not listed in the checklist will generate an error.
- If this option is specified, the file options become checklists. Each checklist should contain hash results, which will be verified against the specified paths. Both normal (BSD) and reverse (GNU) forms are supported in either hexadecimal or base64 format. Output consists of the digest used, the file name, and an OK, FAILED, or MISSING for the result of the comparison. Entries in normal format can be validated using any of the supported checksums (see cksum(1)). Entries in reverse format are validated using the default algorithm. If no file is given, stdin is used.
- Place the checksum into hashfile instead of stdout.
- Echo stdin to stdout and append the checksum to stdout.
- Only print the checksum (quiet mode) or if used in conjunction with the
-cflag, only print the failed cases.
- Reverse the format of the hash algorithm output, similar to the output format used by cksum(1) (but without the number of octets). This is also the format used by the GNU cksum(1) utility.
- Print a checksum of the given string.
- Run a built-in time trial. Specifying
-tmultiple times results in the number of rounds being multiplied by 10 for each additional flag.
- Run a built-in test script.
These utilities exit 0 on success, and >0 if an error occurs.
R. Rivest, The MD5 Message-Digest Algorithm, RFC 1321, April 1992. J. Burrows, The Secure Hash Standard, FIPS PUB 180-1.
D. Eastlake and P. Jones, US Secure Hash Algorithm 1 (SHA1), RFC 3174, September 2001. Secure Hash Standard, FIPS PUB 180-2.